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In the live-action film "Ben 10: Race Against Time", he is depicted as a new-age style parent who wants Ben to have his "freedom," insisting on being called "Carl", not "daddy", "dad" or "father", and letting Ben run off on mysterious adventures without asking questions. Carl wants his wife to give their son some freedom. He seems to be even more laid back than his wife, and is seen at least twice telling her to let Ben have his fun. For instance, near the end when Ben's mother tells him to not eat too much cheese, Carl says to "Let the kid live a little. Eat all the cheese you want, Ben!"

In his first animated appearance, "Goodbye and Good Riddance", he is shown to resent his father, Max Tennyson, as his work as a plumber (the sanitary kind) prevented him from spending time with his family. He finds out about The Plumbers and the Omnitrix the hard way when Vilgax destroys their house and holds him hostage, leading to Ben as Cannonbolt saving him. He later assists Ben, Gwen, and Max in defeating Vilgax, and inside a gutter, he turns gas pipeline on and sets fire to it while XLR8 saves him and Vilgax is caught in the explosion and is supposedly killed. He offers Max dinner but since Vilgax had destroyed their home he couldn't. Max tells him that he could cook something in the RV. Knowing Max's weird taste for food, he says that it would be better to go to some restaurant.

Carl later appears in the Ben 10: Alien Force episode "Grounded," where he and Sandra Tennyson discover that Ben has resumed his superhero activities alongside Gwen and Kevin. Apparently unable to handle the thought of their son constantly risking his life, and angered about Ben's constant lying about his activities, they ground him, forbid him from using the Omnitrix, and tell Gwen's parents of her super-heroism, resulting in her grounding as well and Kevin being forced to fight the Highbreed alone. Additionally, Carl was furious when he found out his father had something to do with it. When this proves to be too much for Kevin to handle, Ben openly defies his parents and uses the Omnitrix to turn into Humongousaur and break out of the house and help Kevin; through this, they realize just how important Ben is to the world. They later come to help Ben and Kevin fight (shooting a Highbreed Commander with Max's ray gun), and admit that they are proud of Ben, allowing him to resume his super-heroism.